Osteosarcoma: As described above, we are currently writing a Phase II study to test a PD L1 antibody in patients with recurrent osteosarcoma. The study will include built-in genomic and immunologic assessment of patients treated and will be performed at 4 institutions. Our target is to have the study open by January 2016. . Ewings Sarcoma: Based partly on our previous finding of a study of an IGFIR antibody alone in the treatment of Ewing's sarcoma (results published several years ago, the COG has now opened a Phase III study comparing standard chemotherapy to chemotherapy plus an IGFIR Ab in high risk Ewing's sarcoma patients. We have recently established an international consortium to study PARP inhibitors in Ewings sarcoma based on published work of others and our unpublished data suggesting that Ewings tumors may be particularly sensitivie to PARP inhibition. We entered the first 3 patients on this study, on based on early toxicity findings, we have now de-escalated to dose of PARP inhibitor and are currently completing a second cohort of patients entered at this dose. Rhabdomyosarcoma: Based upon our published work showing synergy between Src family kinase inhibitors and IGFIR inhibitors in rhabdmyosarcomas, we are currently writing a study to test the combination of dasatinib, a SRC family kinase inhibitor, with an IGFIR Ab. Our target is to have this study open by January 2016. Pediatric Gastrointestinal Stromal Tumors (GIST): We have continued our program to study pediatric GIST patients, a very rare disease that is biologically distinct from adult GIST patients. Our clinics at NIH bring in patients from across the country as well as physicians with interest/expertise in this rare disease from several centers across the country including surgeons, pediatric and medical oncologists as well as pediatric endocrinologists. Following up on our initial observation of germline mutations in SDH genes in sporadic pediatric GIST patients, we have now shown that the majority of tumors studied to date harbor mutations in one of the SDH A B C or D genes and it appears that around 80% of these patients harbor germline mutations in these genes. In addition, we have now shown that a number of patients with SDH deficiency but no identifiable mutation have a tumor-specific methylation of their SDHC promoter leading to silencing of SDHC expression. We have furthermore shown that all of these SDH-deficient GISTS also have global hypermethylation in the tumor genome. Based on responses of SDH mutant kidney cancers to VEGFR inhibitors such as vandetanib we opened a clinical study to test this drug in SDH mutant GIST tumors as well. We are also discussing with CTEP the feasibility of testing a demethylating agent in patients with progressive SDH deficient GIST.